From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Fri, 19 Apr 2013 10:27:52 +0100 Subject: [RFC] arm64: Early printk support for virtio-mmio console devices. In-Reply-To: References: <1366264344-28025-1-git-send-email-pranavkumar@linaro.org> <20130419090558.GA13283@mudshark.cambridge.arm.com> Message-ID: <20130419092752.GB13283@mudshark.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Apr 19, 2013 at 10:25:35AM +0100, Pranavkumar Sawargaonkar wrote: > On 19 April 2013 14:35, Will Deacon wrote: > > On Thu, Apr 18, 2013 at 09:48:49AM +0100, Pranavkumar Sawargaonkar wrote: > >> Actually i thought adding a config register will be easier to add a > >> code than writing entire emulation as 8250 emulation will require to > >> deal with dealing with more registers and more code. > > > > kvmtool already has an 8250 emulation! All we need to do is hack together > > something which will allow us to instantiate those ioport devices in a more > > flexible manner (namely, inside the MMIO space for ARM). For earlyprintk, I > > suspect we can get away without an interrupt too, which should simplify > > things a bit to start with. > > > > Regardless of the outcome of this discussion, I think getting the 8250 > > working on ARM is definitely something worth doing. If I get time, I'll take > > a look. > > I am not against using 8250 emulation (as far as it solves printk > issues for kernel booting logs), but my point is why not to add early > read-write support for virtio console, which also can be useful in > emulation less mach-virt environment also ? We can have both, but only one of those requires a change to the virtio specification. Will